Effect of Electropulsing Current Density on the Strength-Ductility Synergy of Extruded Mg-6Al-1Zn Alloy

The difficulty in enhancing both tensile strength and ductility is limiting the development of high-performance Mg alloys. The "plastic deformation + electropulsing (EP) treatment" is an effective process for modifying the microstructure and enhancing the mechanical properties of metals. In this work, the influence of the current density of EP treatment on the microstructure and tensile property evolution of the as-extruded Mg-6Al-1Zn alloy was systematically investigated. The microstructure of the as-extruded sample was predominantly composed of an α-Mg matrix and a minor quantity of the β-Mg₁₇Al₁₂ phase on grain boundaries. After EP treatments, the microstructure underwent recrystallization, resulting in the formation of fine recrystallized grains. Meanwhile, the distribution and volume fraction of the β-Mg₁₇Al₁₂ phase demonstrated minor changes. After the 60 cycles of EP with a current density of 1050 A·mm^-2 for a duration of 60 s, the tensile strength and elongation of the as-extruded Mg-6Al-1Zn alloy improved from 260 ± 2.6 MPa and 22 ± 1.3% to 319 ± 3.6 MPa and 23 ± 1.1%, respectively. The results prove the effectiveness of EP treatment in tailoring recrystallization via changing current density.